Lining Up With The Celestial Pole - Meade 80EQ-AR Instruction Manual

Meade instruments 80mm | 3.1" equatorial refracting telescope instruction manual 80eq-ar

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Instruction manual (23 pages)

Table of Contents

Enlarged version

The celestial map also contains two poles

and an equator just like a map of the Earth

(see Fig. 6). The celestial poles are defined

as those two points where the Earth's North

and South poles, if extended to infinity,

would cross the celestial sphere. Thus, the

North Celestial Pole is that point in the sky

where the North Pole crosses the celestial

sphere. The North Star, Polaris, is located

very near the North Celestial Pole.

So just as an object's position on the Earth's

surface can be located by its

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latitude and longitude, celestial objects may

also be located using Right Ascension and

Declination. For example: You can locate

Los Angeles, California, by its latitude (+34°)

and longitude (118°). Similarly, you can

locate the Ring Nebula (also known as

"M57") by its Right Ascension (18hr) and its

Declination (+33°).

• • R R I I G G H H T T A A S S C C E E N N S S I I O O N N ( ( R R . . A A . . ) ) : : This Celestial

version of longitude is measured in units

of hours (hr), minutes (min), and seconds

(sec) on a 24 hour "clock" (similar to how

Earth's time zones ar determined by

longitude lines). The "zero" line was

chosen to pass through the constellation

Pegasus, a sort of cosmic Greenwich

meridian. R.A. coordinates range from 0hr

Fig. 6

0min 0sec to 23hr 59min 59sec. There are

24 primary lines of R.A., located at 15-

degree intervals along the celestial

equator. Objects located further and

further East of the zero R.A. grid line (0hr

0min 0sec) carry higher R.A. coordinates.

• • D D e e c c l l i i n n a a t t i i o o n n ( ( D D e e c c . . ) ) : : This celestial version

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of latitude is measured in degrees, arc-

minutes, and arc-seconds (e.g., 15° 27'

33"). Dec. locations North of the celestial

equator are indicated with a plus (+) sign

(e.g., the Dec. of the North

celestial pole is +90°). Any point on

the celestial equator (such as thee

constellations of Orion, Virgo, and

Aquarius) is said to have a

Declination of zero, shown as 0° 0' 0". All

celestial objects therefore may be located

with their celestial coordinates of Right

Ascension and Declination.